The present invention relates to retainer elements for tools and, in particular, to a split retainer clip detachably mounted on a tool shank for rotatably mounting the tool in a holder.
It has heretofore been proposed to employ split retainer clips for securing tools or bits to holders, as evidenced for example by the disclosures of U.S. Pat. Nos. 3,499,685 issued to Kniff on Mar. 10, 1970 and 3,752,515 issued to Oaks on Aug. 14, 1973. Such retainer clips may be employed in connection with pick-type mining bits for securing the bits to a holder while permitting the bits to freely rotate.
The retainer clip comprises a steel ring which is axially split to form a circumferential gap, enabling the ring to be resiliently compressed. Protuberances or projections are provided on the outer surface of the ring which have inclined forward and rearward surfaces. Such surfaces form cam surfaces which radially compress the ring as it is pushed rearwardly into a receiver hole in a bit holder. When the projections become aligned with an annular retaining groove of the holder, the ring snaps outwardly into the groove to secure the bit to the holder. To remove the bit, forwardly directed forces are applied by a suitable tool to again cause the projections to compress the ring, whereupon the bit is able to be withdrawn from the hole of the holder.
It has been found that when used to secure mining bits in high speed rotary drums, the clips may not be able to withstand forces tending to remove the bit from the holder. In this regard, the typical high speeds of the rotary drum generate substantial centrifugal aforces on the bits, tending to throw the bits from the holder. Also, when the drums are backed-off from the formation being cut, strong frictional or drag forces may be generated by contact of the bits with the formation which tend to pull the bits from the holder.
Another problem which has been experienced involves jamming of the bits within the holder. In this regard, in response to the afore-mentioned centrifugal and frictional forces, a rear abutment part of the bit shank abuts against the clip as the latter attempts to resist the forces. In some instances the abutment part partially wedges itself into the rear end of the clip, causing the ends of the clip, i.e., the spaced gap-forming edges, to become jammed between the outer wall of the abutment part and the inner wall of the hole of the holder. As a result, it becomes extremely difficult, if not impossible, to remove the bit for replacement at the job site.
It is, therefore, an object of the present invention to minimize or obviate problems of that sort.
Another object is to prevent the clip from becoming jammed between the bit and the hole of the holder.
An additional object is to maximize the loads which the clip can sustain before allowing removal of the bit.